Jaywalker9988, a member of the Chronic Dev Team confirms that the Greenpois0n RC5, the upcoming untethered iOS 4.2.1 jailbreak, will support customized/animated boot logo on iPhone, iPad and iPod Touch. This new feature, in Greenpois0n RC5, will let you replace Apple boot logo with a video or an animated logo.

So when you go to the greenpois0n website and click the windows download it takes you to “http://www.greenpois0n.com//dl/greenpois0n-win_rc5.zip”. The link is set up for rc5. But the link is down. Now when you try to download the Mac version, the link is functional.